Recently, energy saving is generally required for various apparatuses such as Energy Star according to a rise in the awareness of the global environmental issue and the energy issue. This is not exceptional for wireless communication apparatuses and reduction of power consumption is required during wireless communication.
Here, in a wireless communication method such as a Wireless LAN (Wireless Local Area Network), for example, it is generally possible to perform connection always at a possible highest speed by dynamically changing communication speed according to a radio wave state.
PTL 1: Japanese Laid-Open Patent Publication No. 2003-169363
PTL 2: Japanese Laid-Open Patent Publication No. 2004-356855
The power consumption during wireless communication, however, is generally different depending on a communication standard, a communication mode, a wireless transmission rate, and the like. For example, in the high speed communication of IEEE 802.11n using a MIMO (Multi Input Multi Output) technique, power consumption of a control chip is increased by several hundred milli-watts during wireless communication compared with conventional IEEE 802.11a, 802.11b, 802.11g, and the like. In addition, the power consumption is further increased in the operation of the high-throughput mode (HT40) using a bandwidth of 40 MHz which is twice the conventional bandwidth.
Here, when high-speed communication is always required, it is effective to always use such a high-speed technique. However, there is a problem that it consumes useless power and is not preferable from the viewpoint of energy saving to keep a state in which high-speed communication with a high power consumption is possible, although such a communication method does not always provide high-speed data communication and communication in which high-quality assurance is required (further, data communication itself) in a network using wireless communication.